The objectives of this research proposal are to utilize methods of quantifying placental function which provide kinetic dimensions of utero-placental function. By determining the rate of utilization of a maternal plasma prehormone uniquely by the placenta, a dynamic test of placental metabolism has been formulated. The utility of a dynamic test of placental function as opposed to the primarily utilized determinations of static concentrations of placental hormones in various sources of biologic fluids is that it circumvents the hazards of interpretation resident in static measurements. Further, this proposal will address questions related to the alterations in the kinetics of utero-placental function consequent to physiologic aberrations, pathologic pregnancy and pharmacologic intervention. Through the quantitative assessment of factors which favorably or unfavorably affect placental function, more rational approaches to an improvement of the intrauterine environment of the fetus, particularly of the fetal patient at high risk, may be formulated on scientific rather than intuitive or empiric grounds.